As one method for fastening a plurality of fastened parts together, there is the method of using bolts to fasten the fastened parts together. When using a bolt to fasten fastened parts together, in particular using a bolt to fasten fastened parts together so as to prevent slip between fastened parts by frictional grip connection of the fastened parts when a shear force acts, it is important to stabilize the force in the bolt axial direction caused by the fastening of the bolt (hereinafter referred to as the “bolt axial force”) high. When the bolt axial force caused by fastening of a bolt is small, sufficient frictional grip connection is not caused between the fastened parts and slip occurs between the fastened parts when the fastened parts receive shear force. This causes rotation and loosening of the bolt and as a result there is for example a strong possibility of problems such as detachment of parts and leakage of liquid due to poor adhesion at the joined faces of the fastened parts.
To keep the bolt axial force caused by fastening a bolt constantly stable, it is known to coat the thread of a bolt with a friction coefficient stabilizer (see Japanese Patent Publication (A) No. 9-40991). Japanese Patent Publication (A) No. 9-40991 shows that by coating a friction coefficient stabilizer on a thread or other fastening member, it is possible to stabilize the coefficient of friction at the time of fastening of the thread and possible to impart any value of coefficient of friction and possible to eliminate problems such as looseness or breakage of fastening members such as threads.